The present disclosure relates generally to the field of polymerization and, more specifically, to polystyrene resins.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
As technologies for producing polymeric materials from simple molecular building blocks (i.e. monomers) have advanced, the products of such techniques, such as plastic goods, have become increasingly prevalent in society. One general class of polymeric materials that has seen widespread use is polystyrene. Because of the number of ways in which it may be processed, polystyrene can take a wide variety of forms and, therefore, is found in a wide variety of markets ranging from food contact applications to electronics. General purpose polystyrene (GPPS), for example, is used in a number of every day products such as jewel cases for electronic storage media (e.g. compact discs, digital video discs), housings for electronic components, laboratory equipment, appliances, toys, food containers, disposable cutlery, foams used in coffee cups and packing materials, and so on.
Due to such widespread use, many millions of tons of polystyrene are produced each year in order to manufacture these and other polystyrene-based products. In the interest of environmental stewardship, it would therefore be advantageous if at least a portion of these polystyrene-based products could be recycled. One general source of polystyrene that could potentially be recycled can be obtained from articles of manufacture used by consumers, also known as post consumer recycled (PCR) material. Unfortunately, a number of variables affect the feasibility of using post consumer material as a recycled material source for polystyrene.
For example, forming a new article partially or entirely from PCR polystyrene is generally very difficult. This difficulty mostly arises from poor processability, which is typically a result of the low molecular weights associated with PCR polystyrene resins compared to virgin polystyrene resins (e.g. resins that have not yet been formed into an article). Because of this low molecular weight, articles formed using PCR polystyrene generally also have relatively poor performance (e.g. strength) and poor appearance (e.g. clarity, color).
Processability, performance, and appearance may also be negatively affected by the presence of other materials often associated with polystyrene-based products. For example, polystyrene-based food containers, beverage containers, and/or disposable utensils may contain residual food. Coat hangers, electronic devices such as computers and household appliances, and electronic housings may include metals and/or other polymeric materials. Other polymeric materials commonly associated with used polystyrene-based articles can include polyethylene, polypropylene, polycarbonate, polybutadiene, polyacrylonitrile, and the like, which can all negatively affect the properties of a polystyrene resin.
Unfortunately, the presence of any one or a combination of these materials, and the poor processability, performance, and appearance generally associated with PCR polystyrene can be a significant hindrance to recycling polystyrene products. Accordingly, a need exists for systems and methods for producing a high quality stream of PCR polystyrene, as well as systems and methods for recycling PCR polystyrene into a resin having processability, performance, and appearance suitable for the production of articles of manufacture.